Published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, a journal of the Alzheimer’s Association, the research finds that features of early adversity such as financial difficulty, time spent in hospital, parental unemployment and lower parental education are linked to more rapid cognitive decline as we get older.
Lead author Dr Ruby Tsang, a postdoctoral researcher at the University of Oxford, said: ‘Our socioeconomic status is closely intertwined with many aspects of our lifestyle and is particularly associated with our risk of various health conditions as we age. This research suggests that, even in childhood, these experiences have a far-reaching and important influence on our cognitive performance.
‘The effects of childhood socioeconomic deprivation can last into middle age and late adulthood, with those of lower childhood socioeconomic status less resilient to cognitive decline. Reducing social inequality early in life may have important effects on dementia prevention.’
The research team analysed data in over 15,000 participants from three population studies (the Whitehall II Study, the Health and Retirement Study, and the Kame Project) within the DPUK Data Portal. The DPUK Data Portal is a free-to-access repository and analysis resource containing health research records for over 3.5 million people across more than 50 cohort studies.
Participants had completed self-report questionnaires on their early-life experiences and carried out repeated thinking tests known as cognitive assessments. These tasks assessed overall brain function as well as features including memory, attention, language, and verbal fluency.
The researchers categorised the patterns of cognitive decline in the data, identified three types of trajectory (resilient, gradual age-related decline, and rapid decline), and analysed the association between these cognitive trajectories and early childhood experiences.
Corresponding author Dr Sarah Bauermeister, Senior Scientist and Data Manager at Dementias Platform UK, said: ‘By applying sophisticated statistical models which take into account how subgroups of participants perform on individual cognitive tasks over time, we were able to look more closely at the effects of lower childhood socioeconomic status on later-life cognitive trajectories.’
Previous studies have either focused purely on cognitive performance later in life or the overall pattern of cognitive decline in the population, rather than subgroups showing different patterns of cognitive decline as we age, adding to this paper’s novelty.
For measures of verbal fluency, a small group of participants displayed a ‘curvilinear’ trajectory – a slight increase in cognitive abilities before a sharp decline. This could be due to the ‘practice effect’, whereby subjects need more time to understand a task at first, then perform better when they are familiar with it on the next time of trying. The authors suggest the marked practice effect seen in this small group could be used as an early indicator of impending cognitive decline.
Temporary episodes of adversity appeared to be more strongly associated with a decline trajectory than continual adversity. This could mean that sudden adverse psycho-social incidents (such as parental divorce) have a greater influence on cognitive decline than prolonged socioeconomic deprivation.
The association between early childhood adversity and faster cognitive decline could, the researchers say, be due in part to the prolonged high levels of stress hormones called glucocorticoids in the brain that result from adverse experiences. The researchers call for greater consideration from policymakers of the lasting effects of early childhood adversity.
Professor John Gallacher, study co-author and Director of Dementias Platform UK, said: ‘Research suggests that up to 40% of dementia cases could be prevented by addressing modifiable risk factors. This study shows how important it is for individuals and societies to think about protecting brain health across the lifespan.’